Reference
Circle of Fifths & Key Signatures
Interactive circle of fifths with all 15 major and minor key signatures, relative keys and the order of sharps and flats.
How to use the circle
Moving clockwise adds one sharp (or removes one flat): C → G → D → A… Moving anticlockwise adds flats: C → F → B♭ → E♭… The inner ring shows each key's relative minor, which shares its key signature. Neighbouring keys differ by a single note, so they are the most closely related — which is why music so often modulates to the dominant (one step clockwise) or subdominant (one step anticlockwise).
Order of sharps: F C G D A E B (“Father Charles Goes Down And Ends Battle”). Order of flats: B E A D G C F (the same sentence backwards).